Traditionally, home and business establishments are generally constructed with a majority of 120 VAC power outlets, with 240 VAC power outlets installed more sparingly due to the fact that 240 VAC power requiring devices are less common in the home or in most business environments. Nonetheless, more and more, most modern clothes dryers as well as many other home appliances have greater power requirements forcing consumers to find solutions to the general lack of 240 VAC outlets in most homes.
Further, the advancement of electrical and battery technology in the automobile industry has brought further challenges to consumers who seek affordable and easy ways of charging the batteries of their plug-in automobiles. Although modern plug-in automobiles generally can be charged employing 120 VAC power outlets, the process often requires hours of charging time, most often requiring consumers to charge their vehicle batteries overnight in order to get and keep adequate charge for the following day's commute.
One well known route in enabling the use of 120 VAC power for 240 VAC needs arises in the use of so-called “step-up” transformers or converters. However, such technology only acts to transform DC power to AC, or vice versa. Boost or “step-up” and “step-down” converters include for example, a DC to DC power converter that allows an output voltage greater than its input voltage. The technology generally exists as a class of switched mode power supply (SMPS) containing at least two semiconductors (a diode and a resistor) and at least one energy storage element, such as for example a capacitor, inductor or a combination of the two. Filters made of capacitors, sometimes in combination with inductors, are normally added to the output of the converter to reduce output voltage to ripple.
AC to DC power converters with PFC capability are also desirable in some applications including for example, in laptop and desktop computers or other electronic devices. For instance, U.S. Pat. No. 7,746,040 describes an input shaping AC to DC converter with PFC front end that reduces harmonic components.
U.S. Pat. No. 4,386,394 to Kocher describes a single phase and three phase AC to DC converter. In particular, the patent discloses a single phase AC to DC power converter that accepts a single AC line input voltage and provides a DC output voltage. Input current feedback is used to control the converter and to provide sinusoidal line currents in phase with the applied line voltage. The patent also describes a three phase AC to DC converter as a delta connection of three isolated single phase e. In another embodiment, a three phase AC to DC converter is realized as a delta connection of three isolated single phase AC to DC converters. Reduction in peak transistor currents of the switching transistor in each single phase converter is accomplished by the introduction of third harmonics to each of the single phase AC to DC power converters, Each of the three single phase AC to DC converters are synchronized so that the current pulses at the outputs of the three AC to DC converters are staggered in time reducing the amount of filtering required at the load. However, the device fails to provide a means which allows a user to access 240 VAC in the circumstance in which only 120 VAC power is available
The invention detailed herein is intended to solve a problem faced by homeowners and workers in many professions: Namely, how can a user power equipment that requires 240 VAC in a space that is wired to provide only 120 VAC. As known in the art, VAC is short for Volts of Alternating Current. Alternating current refers to the fact that in the U.S. electrical power is distributed so that the voltage on any supply line is not constant but varies up and down sinusoidally, assuming both positive and negative values in a pattern that repeats 60 times per second. As the voltage varies, so does the current, which is the flow of electrons; thus the term alternating current. Also, one may sometimes see distribution voltages quoted as 110 VAC and 220 VAC.
Utilities have a degree of leeway in the voltages they provide, both as a policy and as a hedge against severe load conditions. When consumers are demanding more electrical power than the utility can provide, one strategy is to reduce the voltage on the distribution grid, thus supplying everyone with slightly less power uniformly. This gives rise to the term “brown-out”. Another strategy that comes into play occurs when a utility wishes to increase the power distribution capacity of its grid without installing thicker and more expensive wires, they may choose to raise the supplied voltage. This is done very slowly, over years or decades, as older, lower voltage consumer equipment is replaced. In any case, for the purpose of this application and specification, 120 VAC is synonymous with 120 VAC and 240 VAC is synonymous with 240 VAC; the invention works the same for any voltages within that range.
Electrical power from utilities in the U.S. commonly is provided as two separate 120 Volt circuits. This is true in essentially all residential homes and apartments, nearly all white-collar businesses, and even in factory spaces where the need for large amounts of electrical power has not been anticipated. The reason for this actually lies with utility customers that have heavy industrial electric power requirements. For supply of large amounts of electrical power, three electrical circuits are provided. This is not simply to have an additional electrical conductor, but instead, with three circuits, it is possible to arrange the relative phases of the three circuits (the points in time where the supplied voltage peaks) each one-third of a cycle apart so that the power available to equipment is constant, not varying up and down 60 times per second with the voltage. This is not possible with any arrangement of one or two AC circuits. For customers that do not require large amounts of uniform power, two of the three phases are routed to their home or business. By distributing different pairs of phases to various locations, the total amount of power supplied by all phases remains balanced.
Though two electrical power phases are wired to nearly all homes and businesses, common wall outlets all provide 120 VAC. Again, to maintain balance in the distribution system, some outlets are wired to one phase and some are wired to another phase. Over many outlets and customer locations, the load will be balanced. Occasionally, one may see in a home or business an outlet of a different design that is wired to both phases and can supply 240 VAC. Typically, in a home, this can be found where an electric clothes dryer, for example, are installed. This outlet is specifically designed not to accept plugs from equipment intended for 120 VAC since that would almost certainly damage the equipment and potentially create a risk of electrical fire.
In attempting to address these shortcomings, the electrical industry has responded with technology that hopes to assist consumers in better utilizing existing electrical infrastructure for higher power-demanding equipment and appliances. To date however, shortcomings in the addressing these needs remain.
The problem the present invention is intended to address arises when a homeowner or business person wishes to operate a piece of equipment that requires 240 VAC but only 120 VAC outlets are available for use. Some homes and many businesses are constructed without any 240 VAC outlets, particularly if they are older. In other cases, the 240 VAC outlet that is available may already be occupied by another piece of equipment, or may be in an inconvenient location. A rapidly growing requirement for 240 VAC comes from electric vehicle quick-chargers. These accessories allow the vehicles' batteries to be recharged in about half the time taken by 120 VAC charging. Other common equipment that can require 240 VAC includes welders, heaters, compressors, and large motors such as on wood chippers.
One might expect that if some outlets in a home are wired to one 120 VAC phase and some are wired to another phase, it would be a simple matter for the homeowner to combine them however, any attempt to do this by an untrained person is likely to result in situations ranging from blowing electrical breakers to fires to electrocution. Even trained professionals need to make careful measurements before proceeding. In addition, having a professional install a new 240 VAC outlet can be prohibitively expensive.
The present invention further employs electrical relays which are generally known in the art however, the following provides a general description of electrical relays that are encompassed within the present invention. The list is not exhaustive and other electrical relays known in the art and not described herein are also encompassed within the scope of the invention.
When an electric current is passed through the coil it generates a magnetic field that activates the armature, and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.
When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper “shading ring” can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.
A latching relay (also called “impulse”, “keep”, or “stay” relays) maintains either contact position indefinitely without power applied to the coil. The advantage is that one coil consumes power only for an instant while the relay is being switched, and the relay contacts retain this setting across a power outage. A latching relay allows remote control of building lighting without the hum that may be produced from a continuously (AC) energized coil.
In one mechanism, two opposing coils with an over-center spring or permanent magnet hold the contacts in position after the coil is de-energized. A pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay off. This type is widely used where control is from simple switches or single-ended outputs of a control system, and such relays are found in avionics and numerous industrial applications.
Another latching type has a remanent core that retains the contacts in the operated position by the remanent magnetism in the core. This type requires a current pulse of opposite polarity to release the contacts. A variation uses a permanent magnet that produces part of the force required to close the contact; the coil supplies suffienct force to move the contact open or closed by aiding or opposing the field of the permanent magnet. A polarity controlled relay needs changeover switches or an H brig drive circuit to control it. The relay may be less expensive than other types, but this is partly offset by the increased costs in the external circuit.
In another type, a ratchet relay has a ratchet mechanism that holds the contacts closed after the coil is momentarily energized. A second impulse, in the same or a separate coil, releases the contacts. This type may be found in certain cars, for headlamp dipping and other functions where alternating operation on each switch actuation is needed.
All three of these basic types of latching relay are currently available and widely used. A stepping relay is a specialized kind of multi-way latching relay designed for early automatic telephone exchanges. An earth leakage circuit breaker includes a specialized latching relay. Very early computers often stored bits in a magnetically latching relay, such as ferreed or the later memreed in the lESS switch.
A reed relay is a reed switch enclosed in a solenoid. The switch has a set of contacts inside an evacuated or inert gas-filled glass tube which protects the contacts against atmospheric corrosion; the contacts are made of magnetic material that makes them move under the influence of the field of the enclosing solenoid or an external magnet.
Reed relays can switch faster than larger relays and require very little power from the control circuit. However, they have relatively low switching current and voltage ratings. Though rare, the reeds can become magnetized over time, which makes them stick ‘on’ even when no current is present; changing the orientation of the reeds with respect to the solenoid's magnetic field can resolve this problem.
Sealed contacts with mercury-wetted contacts have longer operating lives and less contact chatter than any other kind of relay. The mercury-wetted relay has one particular advantage, in that the contact closure appears to be virtually instantaneous, as the mercury globules on each contact coalesce. The current rise time through the contacts is generally considered to be a few picoseconds, however in a practical circuit it will be limited by the inductance of the contacts and wiring. It was quite common, before the restrictions on the use of mercury, to use a mercury-wetted relay in the laboratory as a convenient means of generating fast rise time pulses, however although the rise time may be picoseconds, the exact timing of the event is, like all other types of relay, subject to considerable jitter, possibly milliseconds, due to mechanical imperfections.
The same coalescence process causes another effect, which is a nuisance in some applications. The contact resistance is not stable immediately after contact closure, and drifts, mostly downwards, for several seconds after closure, the change perhaps being 0.5 ohm.
A mercury relay is a relay that uses mercury as the switching element. They are used where contact erosion would be a problem for conventional relay contacts. Owing to environmental considerations about significant amount of mercury used and modern alternatives, they are now comparatively uncommon.
A polarized relay places the armature between the poles of a permanent magnet to increase sensitivity. Polarized relays were used in middle 20th Century telephone exchanges to detect faint pulses and correct telegraphic distortion. The poles were on screws, so a technician could first adjust them for maximum sensitivity and then apply a bias spring to set the critical current that would operate the relay.
A machine tool relay is a type standardized for industrial control of machine tools, transfer machines, and other sequential control. They are characterized by a large number of contacts (sometimes extendable in the field) which are easily converted from normally-open to normally-closed status, easily replaceable coils, and a form factor that allows compactly installing many relays in a control panel. Although such relays once were the backbone of automation in such industries as automobile assembly, the programmable logic controller (PLC) mostly displaced the machine tool relay from sequential control applications.
A contactor is a heavy-duty relay used for switching electric motors and lighting loads, but contactors are not generally called relays. Continuous current ratings for common contactors range from 10 amps to several hundred amps. High-current contacts are made with alloys containing silver. The unavoidable arcing causes the contacts to oxidize; however, silver oxide is still a good conductor. Contactors with overload protection devices are often used to start motors. Contactors can make loud sounds when they operate, so they may be unfit for use where noise is a chief concern.
A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings. A contactor is controlled by a circuit which has a much lower power level than the switched circuit.
A solid state relay or SSR is a solid state electronic component that provides a similar function to an electromechanical relay but does not have any moving components, increasing long-term reliability. A solid-state relay uses a thyristor, TRIAC or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits.
As described herein, the present invention addresses a long standing need and enables a user to convert 120 VAC power, available in any home or structure, so that the power can be used and routed to a 240 VAC outlet to power 240 VAC requiring devices and appliances. With increased use of charging equipment the need to use 120 VAC available power has similarly risen. Presently, plug-in vehicles for example, can be charged using a single 120 VAC outlet however, the charging process is lengthy and often impractical. 240 VAC available power would greatly decrease charging time for plug-in hybrid vehicles however, very few homes or structures are equipped with 240 VAC outlets that aren't already being used for some other dedicated piece of equipment such as a washer, dryer or refrigerator. In other words, even when a home or structure possesses 240 VAC outlets, there are very few available for use. And those that are present are typically dedicated to 240 VAC requiring appliances once the home is built, leaving individuals no 240 VAC available for a user such as for example, in charging a plug-in vehicle or other charged piece of equipment.
Accordingly, difficulties in the field of electrical devices that enable the use of 120 VAC power as a means for powering 240 VAC power requiring devices remain. Existing solutions fail to address particular deficiencies that confront businesses and consumers seeking alternatives to the existing art and a solution to advancing cost and time saving measures for greater implementation of energy options remains elusive. The present invention seeks to address these shortcomings.